This Core is essential for the delivery of optimal veterinary care and facilities utilized for the conduct of in vivo experimentation. The PI.'s of this program project will have access to the Division of Comparative Medicine's AAALAC accredited, centrally managed and operated 125,000 sq. ft. of space, located in five buildings at the Institute. Each of the units has been built or extensively renovated in the last eight years. Four of these buildings have three corridor systems and three have specialized bio- containment units for infectious or hazardous chemical experimentation. Barrier facilities for housing specific pathogen free transgenic mouse colonies are also available. These animal facilities provide MIT investigators a controlled environment with the necessary space, equipment, and containment facilities for performing biomedical related research in animals including germ-free work and also ensures personnel safety during the experimental process. The DCM Comparative Pathology Laboratory will also provide the personnel and expertise to perform histological and immunocytochemical analysis of animal tissues derived from in vivo studies performed within the framework of the program project. Specifically the role of the Core is to provide facilities, equipment, and personnel with expertise to centrally manage and supervise animal husbandry and experimental animal manipulations involved in studies conducted within the Core and several Projects. The specific aims are as follows: Specific aim #1. To provide in vivo systems in which to measure biomarkers and mutations. Specific aim #2. To develop new models of chronic inflammation and/or increased cancer risk. Specific aim #3. To maintain and to produce ascites in mice for monoclonal antibody production.